1. Field of the Invention
This invention relates to a method and apparatus for processing video signals by adjusting the contour of a picture, and a video camera.
2. Description of the Related Art
Up to now, attempts have been made for enhancing sharpness of a picture for eking out insufficient characteristics in the high-frequency components of the spatial frequency of the optical or imaging devices by differentiating video signals in both the horizontal and vertical directions for extracting the contour in the horizontal and vertical directions for generating contour enhancement signals and for adding the contour enhancement signals to the original picture signals with a polarity of enhancing the contour of the picture represented by the original video signals.
FIG. 1 shows the basic arrangement of a conventional video signal processing apparatus for enhancing the contour represented by the original video signals. FIGS. 2A to 2H illustrate an example of waveform signals for illustrating the operation of various components of the arrangement shown in FIG. 1.
To a terminal 111 of video signal processing apparatus, shown in FIG. 1, a video signal S11, such as an imaging signal, shown in FIG. 2A, is supplied. The video signal S11, supplied to the terminal 111, is supplied to an input terminal of an addition circuit 114 and to an input terminal of a delay circuit 112.
The delay circuit 112 outputs the signal S11, supplied to its input terminal, after a delay equal to t1 shown in FIG. 2A. The signal delayed from the signal S11 by the delay circuit 112 is a signal S14 shown in FIG. 2D. This signal S14 is supplied to an input terminal of an addition circuit 116, an input terminal of a delay circuit 113 and to an input terminal of an amplifier 119. The signal amplified from the signal S14 by the amplifier 119 is a signal S15 shown in FIG. 2E. This signal S15 is supplied to a non-inverting input terminal of a subtraction circuit 115. The subtraction circuit 115 is comprised of a differential amplifier.
The delay circuit 113 outputs the signal S14 supplied to its input terminal with a delay equal to time t2 shown in FIG. 2A. The signal delayed by the delay circuit 113 is the signal S12 shown in FIG. 2B. The signal outputted by the delay circuit 113 is sent to the other input terminal of the addition circuit 114.
The addition circuit 114 sums the two signals S11, S12 supplied thereto to generate and output a signal S13 shown in FIG. 2C. The signal S13 obtained by the addition by the addition circuit 114 is supplied to the inverting input terminal of the subtraction circuit 115.
The subtraction circuit 115 performs subtraction of the signal S13 from the signal S15 to produce and output a signal S16 shown in FIG. 2F. This signal S16 corresponds substantially to the differentiated signal S11. The subtraction circuit 115 has its output terminal connected to a terminal of a variable resistor RV1 having its other terminal grounded. The signal S16 has its level adjusted to a pre-set level, as shown at a signal S17 in FIG. 2G, by being passed through the variable resistor RV1. The variable amount of the variable resistor RV1 corresponds to an amount of contour enhancement.
The addition circuit 116 sums the signal S14 from the delay circuit 112 to the signal S17 from the variable resistor RV. This enhances the contour of the signal S11 to give a signal S18 shown in FIG. 2H. The signal S18 is subsequently supplied from the terminal 117 to a downstream side circuit.
With the above-described contour enhancement, it is only possible to enhance the contour of the original picture represented by the original picture signal as compared to the contour of the original picture. Thus, for blurring the original picture, an optical filter has conventionally be employed. However, since it is possible with a given optical filter to blur the picture only to a pre-set extent, the contour weakening degree cannot be changed continuously.
Among the various sorts of contour enhancements, there is known such contour enhancement known as detail processing. This processing increases or decreases the amount of contour enhancement only of picture signals of a fixed color hue, such as skin hue. It is similarly not possible with the skin tone detail processing to weaken the picture contour.